ModelAdmin._create_formsets can generate formsets with a 'None-1' prefix, which is ugly

[kamni]

In cases where a programmer overrides BaseFormSet.get_default_prefix, it is possible to return a 'None' value due to programmer oversight. The solution currently in place is to add 'or not prefix' to prevent errors (​https://github.com/django/django/blob/master/django/contrib/admin/options.py#L1565-L1565). However this results in formsets with a prefix like 'None-1', which looks unfinished and is uninformative when looking at the HTML.

A better choice would be to modify line 1563 to read 'prefix = FormSet.get_default_prefix() or "form"', or another default that might indicate to the developer that their code was failing, without generating ugly html.

[Tim Graham]

You don't think ugly HTML indicates that something is amiss? Adding the fallback seems like it would make the problem more transparent. If this is an issue, I think we should fail loudly if get_default_prefix() doesn't return a value.

[Daniele Procida]

Following discussion with Amymeric Augustin and Tim Graham, there are probably more serious issues with admin inline formsets, and the risks/benefits of interfering with an already delicate part of the system suggest it's better left alone for now.